Pivoted breech bolt lock



P 1950 BvMAILLARD 2,522,628

PIVOTED BREECH BOLT LOCK Filed Dec. 24, 1947 2 Sheets-Sheet l I I J A [A \X gl; mm 1 mum VIII: 'Illllllllfl 7111111111111 My F5 2.

INVENTUR BAR/VWFD MAWZAFRD ATTORNEY Sept. 19, 1950 B. MAILLARD PIVOTED BREECH sour LOCK 2 Sheets-Sh eet 2 Filed Dec. 24, 1947 IN VE N TU R BERN/7P0 M/WLLfi/PD, C BY W ATTORNEY Patented Sept. 19, 195fi -.:...v

UNITED STATES ar PIVOTED BREEcH-non'r Loon l Bernard Maillard, Geneva, switfierlaniassignor" to the Society Brevets "'Aero-Mecaniques S. A., Geneva, Switzerland, a. society of Switzerland Application December 24, 1947, Serial No. 799334 In Switzerland July 14, 1945 Section 1, Public Law 690, August 8,1946

' Patent expires July 14, 1965 Claims. (01. 89-496) Some automatic firearms include a breech block moving inside a breech box and a locking device for securing the breech block to the breech box when a shot is fired. Locking of the breech block is generally ensured by a locking member which cooperates with the breech box. Unlocking of the breech block, after firing of a shot, is obtained through a control device including movable parts which act upon the locking member and are operated, for instance, by one or several pistons pushed backward by the powder gases from the gun barrel. The movable parts are generally constituted by one or several sliding pieces disposed laterally of the breech block and movable with respect to both the breech block and the breech box. The center of gravity of thebreech block and the point where said breech block bears against the locking member are generally located in eccentric positions with respect to the gun barrel axis such that the breech block is-subjected, when a shot is fired and during the un-- locking operation that follows, to a rocking torque which creates reactions between the breech block and the breech box. If, as it is the case in the constructions used up to this time, at least a portion of these reactions is transmitted from the breech block to the breech box through the movable parts of the unlocking device, these parts are called upon to overcome a considerable resistance in the course of their displacements for unlocking the breech block. This is due to the fact that in this case the wedging and frictional stresses produced by said rocking torque uselessly' absorb a considerable amount of energy and create risks of jamming of these parts. The object of the present invention is to eliminate these drawbacks. The system according to my invention includes a breech block movable inside a breech box, a locking device for securing the breech block to the breech box when a shot is fired and a control device for unlocking or releasing the breech block after firing of this shot, this control device including sliding pieces movable longitudinally inside a housing provided between the breech block and the breech box. According to my invention, the breech block and the breech box are provided with surfaces adapted to cooperate together to oppose the tendency to rocking of the breech block under the effect of the reactions caused by the firing of the shot, 50

mi 2 A preferred. embodiment. of my inventiomwill be hereinafter described with reference to. the. accompanying drawings given merelyby Wayof. example and in. which:

Fig. 1 is a longitudinal elevational the line 1-1 of. Fig. 2;

Fig. 2. is a horizontal longitudinal section; 1 Fig. 3 i a sectional view on .the line III?III. ofFig.2; Y Fig. 4 is a perspective View on a largerscale of the breech. system.

The breech block-ll is movable longitudinally in'a breech box l2 and can be locked with respect. thereto by means of a locking member l3 adaptedto bear. through anobliquesurface. I 4 on a cross piece fixed with'respect to said breechbox. The breech box is rigidwith a barrel 1 6 including l a cartridge chamber H. .The movable parts of the unlockingdeviceinclude two lateral sliding. pieces 2| each :provided'with arecess and-a transverse. bar. .22. extending between said slidingpieces and connecting them with a firing pin-2 1; Thefront ends of sliding pieces 21 are in contact with two pistons .23 movable in cylinders 24 parallel to the barrel axis and in'comm-unication with the-inside. of saidbarrel; Firing pin 211ssubJected to the action of an axial spring 25and two lateral springsZ-B are-interposed between slid mg pieces 2| and breechblock .l I. Sliding pieces 2l---bear,-throughtheir lower faces 3|, upon surfaces 32 of breech block I I and, through their upper faces 33, against surfaces 34 of breech box l2. The breech block is guided in the breech box, at the bottom, through direct contact with guiding surfaces of the breech box and at the top, indirectly, through sliding pieces 2| the upper faces .33 of which are, as iust above mentioned, guided along correspond-- mg surfaces 34 of breech box [2. However, in the locking position, the breech block is directly and positively connecte d with the breech box owing to the provision in the front part of said breech box of recesses 29 in which the front ends. of parts 32 are engaged. Thus, the rocking torque applied to the breech block is directly. transmitted to the breech box from the time the section .on

shot is fired until the end of the unlocking pe-v riod. Thisprevents-;a nyv possibility of wedging of sliding pieces 2| between breech block I! and breech box l2 for, when the breech block and the breech box are engaged together (the ends of parts 32 being inserted in recesses 29), a certain play is left between the sliding pieces and the breech box, which play permits an easier displacement of the sliding pieces to ensure unlocking.

The system works in the following manner. Immediately before firing, the parts are in the position shown by the drawing, that is to say the breech block II is locked in forward position by the fact that each locking member I3 bears through its face I4 against bolt I5 and is maintained in this position by the corresponding sliding piece 2I which keeps said member I3 applied downwardly.

When the shot is fired, breech block I I is subjected, at the front, to the action of the rearward force exerted by the powder gases from cartridge chamber II, this force passing above the center of gravity of said breech block, and, at the rear to the effect of the frontward reac tion force exerted by locking member I3, this reaction passing below said center of gravity. The couple formed by these two forces tends to rock breech block II so as to lift the front part thereof; This rocking torque is opposed by the reaction'of the surfaces 29 of breech box I2, under which the front ends of the surfaces 32 of breech block II are engaged.

A very short time after the shot is fired, pistons 23 are pushed rearwardly by the pressure of the powder gases in the barrel. They transmit this rearward movement to sliding pieces 2|. As soon asathe recesses 20 of said pieces 2I come above locking members I3, these members become free to. pivot upwardly about their front ends engaged in cylindrical bearings 28 of breech block II. Due to the obliquity of surface I4, locking members I3 pivot upwardly to pass upon piece I5; under the effect of the reaction exerted by said piece. This unlocks breech block II, which can now slide rearwardly under the effect of the pressure of the gases irom cartridge chamber I1. Breech block I I moves together with sliding pieces 2'I which guide it through their upper faces 33 in breech. box I2.

Cooperating surfaces 29 and 32 are in engagement only when the breech block is locked at the front art of the breech box and during the tinlocking period. They permit a satisfactory: working of the unlocking sliding pieces 2| which no longer risk being wedged during their operation by the rocking torque above referred to.

In a general manner, while I have, in the above description, disclosed what I deem to be practical and efiicient embodiments of my invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as com prehended within the scope of the accompanying claims.

What I claim is:

1. In an automatic firearm, the combination of a breech box provided with a housing, a breech block slidable in said housing, means for locking said breech block with respect to said breech box, a control device for unlocking said breech block after a shot is fired, said control device including longitudinally slidable pieces located between said breech block and said breech box, said breech box being provided m able pieces the front wall of said housing with elongated recesses extending in the direction of movement of said breech block and projections at the front end of said breech block: arrangedto engage said recesses in the locked position of the lparts to Oppose rocking of said breech block upon firing of a shot, whereby said slidable pieces are protected. against wedging stresses caused by said rocking.

2. A combination according to claim 1 in which said projections are disposed laterally with respect to said breech block.

3. In an automatic fire arm, the combination of two breech elements, to wit a breech box provided with a housing and a breech block slidable in said housing, means for locking said breech block in front position with respect to said breech box, a control device for unlockin said breech block after a shot is fired, one of said breech elements being provided in its front part with elongated recesses" extending in the direction of. movement of saidbreech block, and projections at the front endof the other breech element arranged to engage said recesses in the locked position of said breech block to oppose tendency thereof to rocking upon firing of a shot.

4. In an automatic fire arm, the combination of two breech elements, to wit a breech box provided with a housing anda breech block slidable in said housing, means for locking said breech block in front position with respect to said breech box, a control device for unlocking, said breech block after a shot is fired, said control device including longitudinally slidable pieces located between said breech block and said breech box, one of said breech'elements being provided in its front part with elongated recesses extending in the direction of movement;

of; said breech bloclqand projections at the front end of the other breech element arranged to engage said recesses in the locked position of said breech block to oppose'tendency thereof to rocking upon firing-of a shot,whereby said slidare protected against wedging v stresses caused bysaid rocking tendency.

5,. In an automatic firearm, the combination of a breech boxnprovidedwith a housing and :a breech block slidable in said h0using,-means for locking-said breech vblock with respect to said: breech box, a control device for unlocking said, breech block after a shot is; fired, said breech; box being providedinits front wall-of said housing with-elongated recesses extending in they die 4 rection of movement of said breech block and prodections 'atthe front end of said breech. block arranged to engage saidrecesses in the locked position of said breech block i'to' oppose tendency thereof to rocking upon-firing of agshot. b

BERNARD MAILLARD.;

REFERENCES CITED The following references are of record in the file of thispatent: I I i UNITED STATES PATENTS Number Name Date, 1

2 ,199,871 Birkigt flinch.-- May 7, 1940s 

